Intermediate-density lipoproteins (
IDLs) belong to the
lipoprotein particle family and are formed from the degradation of
very low-density lipoproteins. IDL is one of the five major groups of lipoproteins (
chylomicrons,
VLDL, IDL,
LDL,
HDL) that enable fats and cholesterol to move within the water-based solution of the bloodstream. Each native IDL particle consists of protein that encircles various fatty acids, enabling, as a water-soluble particle, these fatty acids to travel in the aqueous
blood environment as part of the fat transport system within the body. Their size is, in general, 25 to 35 nm in diameter, and they contain primarily a range of
triacylglycerols and
cholesterol esters. They are cleared from the
plasma into the
liver by
receptor-mediated endocytosis, or further degraded to form
LDL particles.